1. Field of the Invention
This invention relates to an endless track belt assembly for use in a crawler type track mechanism, more particularly to an endless track belt assembly having a rubber endless track belt and a plurality of metal cores of which their respective lower parts are embedded at an equal spaced distance to one another in the rubber endless track belt along the longitudinal direction of the belt.
2. Description of the Prior Art
Heretofore, as a crawler type track mechanism, in construction machines, metallic endless track belt assemblies have been exclusively used. On the other hand, rubber endless track belt assemblies have been used in cultivation machines.
In the metallic endless track belt assembly 1, a plurality of center-flanged bogie wheels 2 or side-flanges bogie wheels 3 used exclusively for the metallic endless track belt assembly 1 have been associated therewith as shown in FIGS. 1A and 1B. On the other hand, in the rubber endless track belt assembly 1'in which a plurality of metal cores 6 are embedded in a rubber endless track belt 4 except for their respective guide lugs 7, a plurality of center-flanged bogie wheels 2 or outside-contacted bogie wheels 5 used exclusively for the rubber endless track belt assembly 1' have been associated therewith as shown in FIGS. 2A and 2B.
In FIGS. 2A and 2B, reference numeral 8 represents a plurality of steel cords embedded in the rubber endless track belt 4 and extending in the longitudinal direction of the belt 4 to reinforce the same.
In recent years, however, it has appeared that the rubber endless track belt assembly has been often used in construction machines also. In case the side-flanged bogie wheels are associated with the rubber endless track belt assembly, it tends to cause a bad condition called a "pitting phenomenon (water insect phenomenon)" on the contact surface of the rubber endless track belt, because outer peripheral surfaces of side flanges of each of the side-flanged bogie wheels are directly thrust-contacted to the contact surface. Therefore, the rubber endless track belt assembly cannot be used for a long time.
On the other hand, in case the center-flanged bogie wheels are associated with the rubber endless track belt assembly, it does not tend to cause the above-described problem, but the following inconveniences are caused.
Namely, since the rubber endless track belt assembly 1' is made to contact at respective top surfaces m, m of the guide lugs 7, 7 of the metal core 6 with roll-contact surface parts of the center-flanged bogie wheel 2 as shown in FIG. 2A, the distance h between the top surfaces m, m of the guide lugs 7, 7 and the steel cords 8 becomes large, and further it is necessary to enlarge the distance g (shown in FIG. 3) between respective guide lugs of two metal cores adjacent to each other embedded in the rubber endless track belt 4.
As a result, the rubber endless track belt assembly causes fluctuation vibrations at non-contacted portions thereof to the bogie wheels and so called as an "inward bending phenomenon" thereat also when the rubber endless track belt assembly is run on a projection such as, for example, a stone, etc. In case of the inward bending phenomenon, thus bent, non-contacted portion between two metal cores adjacent to each other is opened so that one of the center-flanged bogie wheels falls in that portion. As a result, both the guide lugs of such two metal cores adjacent to each other are forcibly kicked off by the "falled-in" bogie wheel when it gets off from the opened portion of the rubber endless track belt assembly, so that the metal cores are peeled off from the rubber endless track belt thereby deteriorating the durability of the rubber endless track belt assembly.
In order to prevent the aforementioned inconveniences from the rubber endless track belt assembly, it is thought to make all of the guide lugs in T-shape and to elongate the longitudinal length f of the top surface m of each guide lug as shown in FIG. 3. In such a structure of the guide lug, however, the distance g between respective guide lugs of two metal cores adjacent to each other is shortened, so that around the periphery of a drive or idler sprocket wheel respective of both edges of the guide lugs adjacent to one another in the longitudinal direction of the belt assembly cause a collision phenomenon. Therefore, the length f of the top surface m of each guide lug can not be enlarged more than a predetermined limited length, so that a reduction of vibrations and an effective prevention of the inward bending phenomenon themselves have their limitations.
In the case where case the outside-contacted bogie wheels are associated with the rubber endless track belt assembly, the aforementioned inconveniences of using the center-flanged bogie wheels do not occur because the roll-contact surface parts of each of the outside-contacted bogie wheels are directly contacted to the inner peripheral surface of the rubber endless track belt. However, the outside-contacted bogie wheels can not be associated with the metallic endless track belt assembly and tend to cause the above-described pitting phenomenon on the contact surface of the rubber endless track belt thereby deteriorating the durability of the rubber endless track belt assembly.